Scientists used
NASA’s MERRA-2
radiation data.
They found that
shortwave radiation
( SW )
has been rising
since the 1980s.
Their new
Nature journal paper,
was published in
Scientific Reports:
Scientists used
radiation records
from NASA to conclude
shortwave (SW) changes
are “mainly determined”
by cloud modulation.
And clouds were
“showing a
declining trend”
from 1984-2014.
Fewer clouds means
less SW radiation
is reflected
back to space,
and more is absorbed
by the Earth’s surface.
The SW increase
has been larger
and faster than
long wave radiation
( LW )
changes during
this same timespan.
Cloud variability
has been the
“main driver”
of these trends.
The recent warming
can mainly be attributed
to cloud modulation.
The greenhouse effect
from CO2 becomes
a question that is
“still open”.
“When reaching
the Earth,
part of the incoming
solar radiation
is reflected off clouds,
and the surface,
as shortwave radiation
( SW ).
Changes in
cloud distribution
or the
surface albedo
( reflectivity )
affect this flux,
and change the
energy balance.
In the last
four decades,
changes in
cloud distribution,
in low-level clouds,
such as subtropical
stratocumulus,
have been
of great importance,
since they have
the ability to reflect
large amounts
of radiation
back to space,
but do not
reduce significantly
the outgoing
terrestrial radiation.”
“Our research
supports the idea
that clouds
and albedo,
which ultimately
determine the
SW radiation,
are variables of the
utmost importance,
for current
climate change,
in agreement with
previous research
about the changes
in stratocumulus or
energy imbalance,
in the last
four decades,
for example.
An increase
in cloud coverage
of 0.1% would,
on average,
lead to a
7% increase in
spectrally integrated
global average
reflectance of
shortwave radiation.”